It is the second time in a week that the ICRC has been forced to turn back to Damascus. On June 21st, its joint team with the Syrian Arab Red Crescent heard shooting as it tried to enter the old city where the agency says hundreds of civilians are trapped by fighting.

Damaged houses are seen in the Sunni Muslim district of Bab Amro in Homs in February of this year Credit: REUTERS/Mulham Alnader

ICRC spokesman Bijan Farnoudi in Geneva declined to provide specifics or apportion blame for the latest setback after the two sides agreed in principle to a humanitarian truce. In a statement the agency said:

"The ICRC and the Syrian Arab Red Crescent are virtually the only humanitarian organisations working in the hardest-hit areas in the country, and safe and unhindered access is thus essential to their work. ICRC and Syrian Arab Red Crescent teams take considerable risks performing their tasks,"

Turkey's National Security Council said it would respond to Syria's "hostile" downing of one of its reconnaissance jets last week with determination but within international law.

The council, made up of the president, senior ministers and military chiefs, said in a statement after a five-hour meeting:

Turkey will act with determination to use all its rights within the international law against this hostile act. the council, made up of the president, senior ministers and military chiefs, said in a statement after a five-hour meeting.

Efforts to evacuate civilians and wounded from the battered Syrian city of Homs failed again when a rescue team could not enter affected areas, the International Committee of the Red Cross (ICRC) has said.

Beatrice Megevand-Roggo, head of ICRC operations for the Near and Middle East, said in a statement that there had been an agreement from Syrian authorities and the opposition for the ICRC team to carry out an evacuation.

But "on the spot, however, agreed-upon conditions were not met and the staff were unable to proceed", she said.